Methods of chemical vapor deposition (CVD) are used to produce thin layers of material during various industrial processes including semiconductor device fabrication. CVD methods involve introduction of vaporized precursor materials into a reactor, adsorption of the vapor precursor materials onto a surface of a semiconductor substrate and eventual incorporation of such precursor materials into solid films.
Sequential introduction of various precursors into a CVD apparatus may result in undesirable mixing of precursors in areas of the apparatus other than on the semiconductor substrate, such as within a common supply line or within the chamber itself. The first precursor material is purged from the chamber after adsorption onto the semiconductor substrate and prior to introduction of a second precursor material to avoid undesirable mixing.
In conventional CVD processes incomplete purging may occur due to precursor material becoming trapped within an area of the reaction chamber. Such incomplete purging may result in unwanted mixing of precursor materials upon the introduction of the second precursor and may lead to adsorption of precursor materials and adduct formation upon reaction chamber surfaces. Adduct materials that form on the reaction chamber surfaces may precipitate onto the substrate and cause defects in the thin layer formation.
Accordingly it is desirable to provide CVD apparatuses and deposition methods that are designed to minimize unwanted mixing and unwanted deposition of films onto apparatus surfaces.